[Boost-bugs] [Boost C++ Libraries] #12998: Can't forward single-argument constructors to sinks

Subject: [Boost-bugs] [Boost C++ Libraries] #12998: Can't forward single-argument constructors to sinks
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2017-04-30 22:25:39

#12998: Can't forward single-argument constructors to sinks
------------------------------+---------------------
 Reporter:  steinar+boost@…   |      Owner:  andysem
     Type:  Bugs              |     Status:  new
Milestone:  To Be Determined  |  Component:  log
  Version:  Boost 1.63.0      |   Severity:  Problem
 Keywords:                    |
------------------------------+---------------------
 CasparCG has code like this:

 ```
         class sink_backend : public
 boost::log::sinks::basic_formatted_sink_backend<char>
         {
                 std::function<void(std::string line)>
 formatted_line_sink_;
         public:
                 sink_backend(std::function<void(std::string line)>
 formatted_line_sink)
                         :
 formatted_line_sink_(std::move(formatted_line_sink))
                 {
                 }

                 void consume(const boost::log::record_view& rec, const
 std::string& formatted_message)
                 {
                         try
                         {
                                 formatted_line_sink_(formatted_message);
                         }
                         catch (...)
                         {
                                 std::cerr << "[sink_backend] Error while
 consuming formatted message: " << formatted_message << std::endl <<
 std::endl;
                         }
                 }
         };
 […]
         auto sink =
 boost::make_shared<sink_type>(std::move(formatted_line_sink));
 ```

 This fails with a long spew of template errors, evidently because for
 single-argument constructors, only variants with named parameters are
 considered (sync_frontend.hpp, BOOST_LOG_SINK_CTOR_FORWARD_INTERNAL_1).
 This is a regression from 1.59.0.

 Adding a dummy int parameter and setting it to 0 makes the code compile.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/12998>
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